1. Technical Field
The present invention relates to a maintenance device for a liquid ejection head provided in a liquid ejection apparatus such as a printer, which performs maintenance for the liquid ejection head, and a liquid ejection apparatus including such a maintenance device.
2. Related Art
A typical ink jet printer (hereinafter referred to as a “printer”), which is one type of a liquid ejection apparatus, includes a recording head (liquid ejection head), which has nozzles for ejecting ink (liquid). Ink is ejected toward a target from the nozzles to perform printing. In such a printer, if ink is not discharged for a long time, the ink may become viscid and solidify in the nozzles of the recording head. This may clog the nozzles. Therefore, in the prior art, a maintenance device is arranged in the printer to carry out maintenance on the recording head (for example, refer to Japanese Laid-Open Patent Publication No. 11-115275).
The maintenance device of the above publication includes a cap and a suction pump. The cap is contactable with the recording head in a manner surrounding the nozzles. The suction pump draws pressure out of the cap when in a state of contact with the recording head to generate negative pressure in the cap. The generation of negative pressure in the cap that is in contact with the recording head achieves a suction cleaning (suction restoration process) that draws ink out of the nozzles. Such suction cleaning eliminates viscid or solidified ink from the nozzles and removes bubbles from the ink. This restores the recording head to a state in which ink can be ejected from the nozzles in a satisfactory manner.
The maintenance device of the above publication also includes a rubber wiper that wipes a nozzle forming surface in which the nozzles of the recording head are formed. The wiper wipes off ink, paper dust, and the like from the nozzle forming surface. Such wiping also shapes the ink in the nozzles to form a meniscus (hereinafter, referred to as a “nozzle meniscus”). Variations in the form of the nozzle meniscus cause variations in the ejected amount of liquid droplets. This results in variations in the size of printing dots and thereby lowers the printing quality. Therefore, by performing wiping and shaping the ink to form a nozzle meniscus, the printing quality is maintained at a satisfactory level.
In the maintenance device described in the above publication, the wiper is formed from rubber. Therefore, as the wiper wipes and slides along the nozzle forming surface of the recording head, the elasticity of the wiper elastically deforms the wiper and displays a wiping force. However, a change in the distance between the nozzle forming surface of the recording head and a platen (so-called platen gap) in accordance with the thickness of the target would vary the position of the nozzle forming surface of the recording head relative to the wiper. As a result, the wiping force, which is dependent on the elasticity of the wiper, may become insufficient for wiping the nozzle forming surface in a satisfactory manner.
To cope with such changes in the platen gap, the maintenance device of the above publication includes a platen gap adjustment mechanism for automatically adjusting the platen gaps in predetermined fixed intervals during wiping. However, the adjustment of the platen gap is performed by vertically moving a guide shaft with the drive force of a motor. The guide shaft supports a carriage, which holds the recording head, so that the carriage is movable back and forth along a main scanning direction. Therefore, the adjustment is difficult and the structure of the maintenance device is complicated.